| Bioethanol | Feedstock |
| 1st generation | Material from agricultural sources comprising the edible parts of plants such as starch and sugar. |
| 2nd generation | Material from agricultural and forestry residues composed mainly of cellulose, such as sugarcane bagasse and wheat straw. |
| 3rd generation | Non-food vegetative material with rapid growth, such as perennial grasses and green algae |